This invention relates to hand stamps and more particularly to a self-inking hand stamp that does not require a stamp pad. The hand stamp utilizes a porous foam layer and an ink cartridge mounted together in intimate contact with each other to create the printing aspect of the device. The porous foam layer has the image forming stamp material on its surface. This invention also relates to the design and manufacture of the stamp frame that adhesively holds the porous foam layer and ink cartridge to the stamp frame.
Many conventional stamps require manufacturing the printing surface from rubber or other flexible material. The printing surface is securely mounted on a handle that is grasped by the user. The printing surface is placed into contact with an inkpad where ink transfers to the printing surface. The inked printing surface is then pressed against the surface onto which the stamp image is to be transferred. Repetition of the stamping process requires that the printing surface be pressed against the inkpad each time an image is to be transferred. This is a disadvantage to the user as it requires extra time for each re-inking step and slows down the stamping process if multiple stampings are to be done. It also requires the use of a separate inkpad that must be periodically re-inked.
An improved stamp was developed that uses a printing surface made from an ink permeable material that allows ink to pass from an ink reservoir, through the printing surface and onto the object being marked. This eliminated the need for a separate stamp inkpad. These stamps are referred to as hand stamps. There is no simpler stamping device to transfer images than the hand stamp.
An example of this stamp is illustrated in U.S. Pat. No. 5,577,444 issued to Toyama. This patent illustrates a hand stamp that has a sealed ink compartment that stores the ink. The ink can be refilled into the compartment by means of removing a threaded screw at the top of the compartment. Once the screw is removed, the ink can be injected, and the screw replaced. The stamping member has a stamping surface with stamping and non-stamping portions. The stamp pad is fixed to the stamp frame at the factory and is not designed to be field installed or removed.
There are several problems with this device. First, the porous foam or printing surface is factory sealed. If an error is made during manufacturing, the entire mount must be thrown away, thus increasing costs. Since it is factory sealed, a special machine is required to expose the porous foam to form the image on the porous foam surface.
Another type of stamp is illustrated in U.S. Pat. No. 5,942,312 issued to Venkataraman et al. This patent discloses a pre-inked thermoplastic foam which has open cells in the area that is designed to transfer ink and closed or sealed cells in the area which is designed to be impermeable to ink. The pre-inked thermoplastic foam is pre-inked before the image is formed on the thermoplastic material. Thus if there is a problem with the image, the entire pad including the ink, is wasted. Furthermore there may be difficulties in forming an image on a pre-inked thermoplastic foam as it may be messy or require special handling due to the ink in the pre-inked thermoplastic foam. The pre-inked thermoplastic foam is mechanically held to the stamp and assembled at the factory. The pre-inked thermoplastic foam is not designed to be installed or removed in the field.
U.S. Pat. No. 5,996,493 issued to Okumura et al. illustrates a pre-inked stamp that uses an ink pack to supply ink to the porous stamp. The ink pack ruptures when the ink pack is pressed against a cutting device in the stamp. There is a transparent film thermally attached to the stamp surface to protect the stamp surface during transport and storage. The transparent film is removed just before using the stamp for printing images. The porous stamp portion is thermally attached to the holder at the factory and is not designed to be installed in the field.
Another stamp is disclosed in U.S. Pat. No. 6,164,202 issued to Takami. This patent discloses a stamp unit comprising a holder, which is placed in a stamp manufacturing device for making a stamping surface on a stamp material. The holder interacts with the stamp manufacturing device to properly position the holder in the manufacturing device. An image is formed on the surface of the stamp forming material by fusing portions on the surface. The stamp forming material is saturated with ink and ink is allowed to flow out from the non fused portions onto a printing sheet forming the image.
A problem not solved by the prior art devices is providing an ink cartridge and stamp in a self contained easy to use unit. Also, the method of manufacturing a hand stamp with an adhesively held ink cartridge was never taught.
A characteristics of the prior art devices is that the stamp forming material with the image to be transferred thereon was held in place in the stamp by means of a trim ring or other mechanical grasping means that generally extended around the circumference of the stamp forming material. When the stamp is assembled, the trim ring snaps into place holding the stamp forming material within the stamp frame. In other devices the stamp forming material is attached to the stamp frame at the factory in such a way that it could not be attached in the field. It would be desirable if the stamp forming material could be held in place by adhesive, thus eliminating one component of the stamp. This would also reduce the cost of the stamp. It would also be desirable if the attachment of the stamp pad to the frame could be done in the field so that expensive equipment and added manufacturing costs could be eliminated.
Applicant's invention addresses and solves the problems of the prior art devices. The invention comprises an ink cartridge that has an ink storage layer or cartridge and a porous foam layer with an image forming stamp material on the surface. The two layers are in intimate contact with each other and are designed for mounting in a hand stamp. The hand stamp has a handle, which is grasped by the user. The image forming stamp material is a porous foam material and has an outer surface made of a porous resin layer. Portions of the porous resin layer are melted and solidify into impermeable areas that are ink impermeable, and other portions of the porous resin layer remain unmelted and allow ink to pass. In this manner the stamping image is defined. There is an upstanding wall or window frame that surrounds the cartridge. This provides an ink reservoir or ink well where ink is poured to saturate the cartridge. The top edge of the upstanding wall is coated with an ink impermeable coating for providing a surface that is receptive to an adhesive placed on it.
A frame member has a top, a bottom and side walls. There is a ledge at the bottom. An adhesive is applied between the ledge and the top edge of the upstanding wall on the cartridge. The ink cartridge is thus affixed to the ledge by means of the adhesive. The coating on the top edge provides a surface that maintains the adhesion between the cartridge and the ledge as it is impervious to the ink.